The Open Source IMS Core was an initiative of the NGNI department in Fraunhofer FOKUS which has provided since 2004 an Open Source implementation of the 3GPP IP Multimedia Subsystem (IMS). It was backed up by the same CND team which started OpenEPC.
The Open Source IMS Core has been used extensively in the last ten years by research projects, vendors and operators. Due to the relevance of IMS for VoLTE (Voice over LTE) and VoWiFi (Voice over Wi-Fi) CND plans to rescue the Open Source IMS Core and update it to the current state of the art as well as offering a product based on its solid acumen in VoIP.
The former web-site of the Open Source IMS Core project can still be found here.